Painful obesity disease mainly manifests as painful nodules or fat masses on top of obesity. Painful obesity is a rare autonomic nervous system disorder of unknown etiology, manifested by abnormal accumulation of subcutaneous fat in certain parts of the trunk and accompanied by spontaneous pain in that area. The disease was first described by Dercum (1892) and is therefore also known as Dercum’s disease. What causes the symptoms of obesity with painful nodules or fat masses? Causes The disease may be associated with metabolic disorders. It has also been reported to be related to immune dysfunction, but this has not been elucidated. The pathogenesis is unknown. In the past, it was thought to be related to hypothalamus and endocrine disorders, but Pimenta et al. (1992) confirmed that the pituitary, adrenal, thyroid and gonadal secretion functions were normal in patients with this disease. The disease may be associated with metabolic disorders. It may cause local pain due to abnormal fat accumulation affecting the dermal nerve, or it may cause hyperalgesia due to degeneration of the dermal nerve. It has also been suggested in the literature that it is related to immune dysfunction, but this has not been elucidated. The disease progresses chronically, often with late onset of psychiatric symptoms such as depression and mental retardation, as well as mental decline with a tendency to progressively develop dementia. The characteristic painful fatty nodules on top of obesity are diagnosed according to age of onset and gender.